The flavonoids in citrus fruits may help ward off neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, which result from the breakdown of cells in the nervous system.

In part, these diseases are caused by inflammation.

Flavonoids found in citrus fruits have anti-inflammatory capabilities that are thought to help protect against the chain of events that causes the nervous system to deteriorate (27, 28).

Specific types of flavonoids, including hesperidin and apigenin, have been shown to protect brain cells and improve brain function in mice and test-tube studies (27).

Several studies in older adults have also shown that citrus juices may boost brain function (29, 30, 31).

Summary: Citrus fruits and juices may help boost brain function and protect the brain from neurodegenerative disorders.

The downside of citrus fruits

While the overall picture of citrus is pretty rosy, there are a few potential downsides.

High amounts could cause cavities

Eating lots of citrus fruits or juices could increase the risk of cavities. That’s because the acid in citrus fruits erodes tooth enamel (32, 33).

This is a particular risk if you sip on lemon water all day long, bathing your teeth in acid.

Interestingly, certain compounds in citrus peels may combat the bacteria that cause dental cavities, although more research is needed to see how that information could be used (34).

Fruit juice isn’t as healthy as whole fruit

While orange and grapefruit juices contain lots of vitamin C and other nutrients often found in whole citrus fruits, they’re not quite as healthy.

That’s because a serving of juice delivers much more sugar and way less fiber than a serving of whole fruit (6, 35).

There are a couple reasons why that’s a problem.

First, more sugar per serving translates to more calories. Drinking fruit juice and other high-calorie beverages can cause you to gain weight (36).

Second, when your body takes in large amounts of fructose (the type of sugar in fruit juice), it is quickly absorbed into your bloodstream and delivered to your liver (37).

If your liver gets more fructose than it can handle, it turns some of the extra fructose into fat. Over time, those fat deposits can cause fatty liver disease (38).

Getting fructose from whole fruit is not a problem, given that you’re getting a smaller amount at a time. Plus, the fiber found in fruit buffers the fructose, causing it to be absorbed more slowly into your bloodstream.

Grapefruit can interact with certain medications

Eating grapefruit or drinking grapefruit juice can be a problem if you take certain medications.

There’s an enzyme in your gut that reduces the absorption of certain medications. Furanocoumarin, a chemical in grapefruit, binds to this enzyme and keeps it from working properly.

As a result, your body absorbs more medication than it’s supposed to (39).

Furanocoumarin is also found in tangelos and Seville oranges (the kind used for marmalade).

There are several prescription and over-the-counter drugs that are affected by grapefruit, including (40):

Some statins, for high cholesterol, including Lipitor and Zocor

Some calcium channel blockers, for high blood pressure, including Plendil and Procardia

Cyclosporine, an immunosuppressant drug

Some Benzodiazepines, including Valium, Halcion and Versed

Other medications, including Allegra, Zoloft and Buspar

Summary: While citrus fruits are generally healthy, they can have some drawbacks. Their acid can erode tooth enamel and grapefruit can interact with some medications.

The bottom line

There are many reasons to eat citrus fruits.

They’re nutritious and contain plant compounds that can protect against a variety of diseases, including cancer, heart disease, brain dysfunction and kidney stones.

But aim to consume whole fruits, rather than a lot of fruit juice, as its high sugar content can lead to problems.

Overall, citrus fruits are healthy, low in calories and convenient to eat. Most people could benefit from adding more citrus to their diet.